diff -r 000000000000 -r 6474c204b198 storage/public/mozStorageHelper.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/storage/public/mozStorageHelper.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,181 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZSTORAGEHELPER_H
+#define MOZSTORAGEHELPER_H
+
+#include "nsAutoPtr.h"
+
+#include "mozIStorageAsyncConnection.h"
+#include "mozIStorageConnection.h"
+#include "mozIStorageStatement.h"
+#include "nsError.h"
+
+/**
+ * This class wraps a transaction inside a given C++ scope, guaranteeing that
+ * the transaction will be completed even if you have an exception or
+ * return early.
+ *
+ * aCommitOnComplete controls whether the transaction is committed or rolled
+ * back when it goes out of scope. A common use is to create an instance with
+ * commitOnComplete = FALSE (rollback), then call Commit on this object manually
+ * when your function completes successfully.
+ *
+ * Note that nested transactions are not supported by sqlite, so if a transaction
+ * is already in progress, this object does nothing. Note that in this case,
+ * you may not get the transaction type you ask for, and you won't be able
+ * to rollback.
+ *
+ * Note: This class is templatized to be also usable with internal data
+ * structures. External users of this class should generally use
+ * |mozStorageTransaction| instead.
+ */
+template<typename T, typename U>
+class mozStorageTransactionBase
+{
+public:
+  mozStorageTransactionBase(T* aConnection,
+                            bool aCommitOnComplete,
+                            int32_t aType = mozIStorageConnection::TRANSACTION_DEFERRED)
+    : mConnection(aConnection),
+      mHasTransaction(false),
+      mCommitOnComplete(aCommitOnComplete),
+      mCompleted(false)
+  {
+    // We won't try to get a transaction if one is already in progress.
+    if (mConnection)
+      mHasTransaction = NS_SUCCEEDED(mConnection->BeginTransactionAs(aType));
+  }
+  ~mozStorageTransactionBase()
+  {
+    if (mConnection && mHasTransaction && ! mCompleted) {
+      if (mCommitOnComplete)
+        mConnection->CommitTransaction();
+      else
+        mConnection->RollbackTransaction();
+    }
+  }
+
+  /**
+   * Commits the transaction if one is in progress. If one is not in progress,
+   * this is a NOP since the actual owner of the transaction outside of our
+   * scope is in charge of finally comitting or rolling back the transaction.
+   */
+  nsresult Commit()
+  {
+    if (!mConnection || mCompleted)
+      return NS_OK; // no connection, or already done
+    mCompleted = true;
+    if (! mHasTransaction)
+      return NS_OK; // transaction not ours, ignore
+    nsresult rv = mConnection->CommitTransaction();
+    if (NS_SUCCEEDED(rv))
+      mHasTransaction = false;
+
+    return rv;
+  }
+
+  /**
+   * Rolls back the transaction in progress. You should only call this function
+   * if this object has a real transaction (HasTransaction() = true) because
+   * otherwise, there is no transaction to roll back.
+   */
+  nsresult Rollback()
+  {
+    if (!mConnection || mCompleted)
+      return NS_OK; // no connection, or already done
+    mCompleted = true;
+    if (! mHasTransaction)
+      return NS_ERROR_FAILURE;
+
+    // It is possible that a rollback will return busy, so we busy wait...
+    nsresult rv = NS_OK;
+    do {
+      rv = mConnection->RollbackTransaction();
+      if (rv == NS_ERROR_STORAGE_BUSY)
+        (void)PR_Sleep(PR_INTERVAL_NO_WAIT);
+    } while (rv == NS_ERROR_STORAGE_BUSY);
+
+    if (NS_SUCCEEDED(rv))
+      mHasTransaction = false;
+
+    return rv;
+  }
+
+  /**
+   * Returns whether this object wraps a real transaction. False means that
+   * this object doesn't do anything because there was already a transaction in
+   * progress when it was created.
+   */
+  bool HasTransaction()
+  {
+    return mHasTransaction;
+  }
+
+  /**
+   * This sets the default action (commit or rollback) when this object goes
+   * out of scope.
+   */
+  void SetDefaultAction(bool aCommitOnComplete)
+  {
+    mCommitOnComplete = aCommitOnComplete;
+  }
+
+protected:
+  U mConnection;
+  bool mHasTransaction;
+  bool mCommitOnComplete;
+  bool mCompleted;
+};
+
+/**
+ * An instance of the mozStorageTransaction<> family dedicated
+ * to |mozIStorageConnection|.
+ */
+typedef mozStorageTransactionBase<mozIStorageConnection,
+                                  nsCOMPtr<mozIStorageConnection> >
+mozStorageTransaction;
+
+
+
+/**
+ * This class wraps a statement so that it is guaraneed to be reset when
+ * this object goes out of scope.
+ *
+ * Note that this always just resets the statement. If the statement doesn't
+ * need resetting, the reset operation is inexpensive.
+ */
+class MOZ_STACK_CLASS mozStorageStatementScoper
+{
+public:
+  mozStorageStatementScoper(mozIStorageStatement* aStatement)
+      : mStatement(aStatement)
+  {
+  }
+  ~mozStorageStatementScoper()
+  {
+    if (mStatement)
+      mStatement->Reset();
+  }
+
+  /**
+   * Call this to make the statement not reset. You might do this if you know
+   * that the statement has been reset.
+   */
+  void Abandon()
+  {
+    mStatement = nullptr;
+  }
+
+protected:
+  nsCOMPtr<mozIStorageStatement> mStatement;
+};
+
+// Use this to make queries uniquely identifiable in telemetry
+// statistics, especially PRAGMAs.  We don't include __LINE__ so that
+// queries are stable in the face of source code changes.
+#define MOZ_STORAGE_UNIQUIFY_QUERY_STR "/* " __FILE__ " */ "
+
+#endif /* MOZSTORAGEHELPER_H */